1. Field of the Invention
The present invention relates to an air-conditioning device for a vehicle.
2. Description of Related Art
An air-conditioning device for a vehicle has a vapor compression refrigerating cycle, and a compressor of the refrigerating cycle is driven by a driving force output from an internal combustion engine of the vehicle. While the air-conditioning device is active, the driving force of the engine is required to be increased, because additional driving force is necessary for the compressor. Therefore, fuel expense is increased while the air-conditioning device is active.
JP-A-2006-298042 discloses an air-conditioning device for a vehicle. A threshold is set for an accelerator opening based on an actual temperature and a preset temperature of a passenger compartment of the vehicle. When the accelerator opening becomes larger than the threshold, power transmission from an engine to a compressor is blocked. Thus, a load of the engine is lowered so as to improve mileage and acceleration characteristic.
However, an output of the engine cannot be controlled in accordance with an output necessary for driving the compressor, while the output of the engine can be controlled in accordance with an output necessary for driving the vehicle. That is, an engine output necessary for an air-conditioning is changed in accordance with a load of the air-conditioning, not in accordance with the accelerator opening.
Therefore, the engine output necessary for the air-conditioning cannot be controlled in JP-A-2006-298042. That is, a fuel consumption amount cannot be controlled in accordance with the load of the air-conditioning.
For example, even if the load of the air-conditioning is lowered, the fuel consumption amount necessary for the air-conditioning cannot be lowered. In this case, the mileage cannot be improved.